KR102092471B1 - Polarizing plate and image display apparatus comprising the same - Google Patents

Abstract

This specification is a polarizer; And a protective layer provided on one or both surfaces of the polarizer in direct contact with the polarizer, wherein the protective layer comprises a polarizing plate and the polarizing plate which is a cured product of a photocurable composition for a polarizing plate protective layer comprising an epoxy compound and an oxetane-based compound. An image display device is provided.

Description

Polarizing plate and image display device including the same {POLARIZING PLATE AND IMAGE DISPLAY APPARATUS COMPRISING THE SAME}

This application claims the benefit of the filing date of No. 10-2017-0122686 filed with the Korean Intellectual Property Office on September 22, 2017, the entire contents of which are incorporated herein.

This specification relates to a polarizing plate and an image display device including the same.

Conventional polarizing plates for liquid crystal displays use a general polyvinyl alcohol-based polarizer, and are configured to attach a protective film such as TAC to at least one side of the polarizer.

Recently, in the polarizer market, the demand for low light leakage and thinning is increasing, and a method of forming a protective film directly on a polarizer is being investigated instead of applying a conventional pre-formed protective substrate to satisfy this property.

However, when the protective film is directly formed on the existing polyvinyl alcohol-based stretched type polyvinyl alcohol-based polarizer, the polarizer is torn due to the stress caused by the contraction of the polarizer at high temperature compared to the case where a protective substrate is applied to both surfaces as in the past. It was difficult to solve the problem that occurred.

Japanese Patent Publication No. 2006-199855

The present specification provides a polarizing plate and an image display device including the same.

This specification is a polarizer; And

A protective layer provided in direct contact with the polarizer on one or both sides of the polarizer,

The protective layer is a cured product of a photocurable composition for a polarizing plate protective layer comprising an epoxy compound and an oxetane-based compound,

In the spectrum by the Fourier transform infrared spectroscopy (FTIR) of the protective layer, the following equation 1 is satisfied,

The thickness of the protective layer is 4㎛ to 11㎛,

In the spectrum by the Fourier transform infrared spectroscopy (FTIR) of the protective layer, to provide a polarizing plate that satisfies the following equation (1).

[Equation 1]

In the above formula 1,

I _e is the ratio of the peak intensity in the protective layer Fourier transform infrared spectroscopy (FTIR) 1740cm ^-1 to 1700cm ^-1 in the spectra due to the peak intensity compared to 920 cm ^-1 to 900cm ^-1 in a,

I _a is the peak intensity in the Fourier transform infrared spectroscopy (FTIR) spectrum 1740cm ^-1 to 1700cm ^-1 1420 cm ^-1 peak intensity compared to 1380cm ^-1 in at by the protective layer.

In addition, the present specification provides an image display device including the polarizing plate described above.

The polarizing plate according to an exemplary embodiment of the present specification has the advantage of replacing the base layer, which requires that the conventional adhesive layer is interposed, with a single coating layer, so that thinning, lightening of the polarizing plate, and minimization of cost and process are possible.

The polarizing plate according to an exemplary embodiment of the present specification has the advantage of little or little phase difference.

The polarizing plate according to an exemplary embodiment of the present specification includes a protective layer having a high tensile elasticity modulus and a storage elastic modulus, and thus has a merit that shrinkage does not occur significantly when curing the photocurable composition for a protective layer to form a protective layer.

In addition, even in a high temperature or high humidity environment, there is an advantage that can suppress the light leakage phenomenon due to shrinkage or expansion of the polarizer.

In addition, since the tensile modulus and tensile modulus of the protective layer have high properties, even if a separate protective film is not included on the protective layer, there is an advantage of having high durability.

The polarizing plate according to an exemplary embodiment of the present specification is excellent in durability under a high temperature environment, and has an advantage of suppressing light leakage when applied to a liquid crystal display having a large area.

In addition, the polarizing plate according to an exemplary embodiment of the present specification can minimize the occurrence of yellowing of the protective layer.

1 shows a polarizing plate according to an exemplary embodiment of the present specification.
2 shows a polarizing plate according to another exemplary embodiment of the present specification.
3 shows a polarizing plate according to another exemplary embodiment of the present specification.
4 is a cross-sectional view showing an example of an image display device according to an exemplary embodiment of the present specification.
5 is an FTIR spectrum of the protective layer of the polarizing plate of Comparative Example 8.
6 is an FTIR spectrum of the protective layer of the polarizing plate of Example 1.

Hereinafter, the present invention will be described.

When a member is referred to as being “on” another member in the present specification, this includes not only the case where one member abuts another member, but also another member between the two members.

In the present specification, when a part “includes” a certain component, this means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

In the present specification, FTIR means Fourier transform infrared spectroscopy (FTIR), and Varian 3100 FT-IR (manufactured by Varian) may be used for measurement.

In the present specification, the "peak intensity at 1740 cm ^-1 to 1700 cm ^-1 " is the peak intensity for the C = O bond of the protective layer, and is used to standardize other peak intensity.

In the present specification, the "peak intensity at 920 cm ^-1 to 900cm ^-1" is the peak intensity of the CO bond of the oxirane group of octanoic cetane compound (CO Stretching of oxirane group) of the protective layer.

In this specification, the peak intensity for the "1420 cm ^-1 to peak intensity at 1380cm ^-1" is = CH-H bond (= CH-H band of acrylate ) of the acrylic compound of the protective layer, the I _e Indicates the presence of an epoxy group in the protective layer, and I _a indicates the presence or absence of an acrylate group in the protective layer.

In this specification, the peak intensity corresponds to the peak area of the FTIR spectrum. For example, the peak area can be derived by direct integration. Alternatively, it is assumed that one peak of the FTIR spectrum is a Gaussian distribution, and the peak area can be expressed as a product of the height of the peak and a half value width.

In the present specification, the peak intensities may be measured before and after curing of the protective layer composition, respectively.

Hereinafter, a polarizing plate according to an exemplary embodiment of the present specification will be described.

According to FIG. 1, a polarizer according to an exemplary embodiment of the present specification includes a polarizer 10; And a protective layer 20 provided on one or both sides of the polarizer 10 in direct contact with the polarizer.

This specification is a polarizer; And

A protective layer provided in direct contact with the polarizer on one or both sides of the polarizer,

The protective layer is a cured product of a photocurable composition for a polarizing plate protective layer comprising an epoxy compound and an oxetane-based compound,

In the spectrum by the Fourier transform infrared spectroscopy (FTIR) of the protective layer, the following equation 1 is satisfied,

The thickness of the protective layer is 4㎛ to 11㎛,

In the spectrum by the Fourier transform infrared spectroscopy (FTIR) of the protective layer, to provide a polarizing plate that satisfies the following equation (1).

[Equation 1]

In the above formula 1,

I _e is the ratio of the peak intensity in the protective layer Fourier transform infrared spectroscopy (FTIR) 1740cm ^-1 to 1700cm ^-1 in the spectra due to the peak intensity compared to 920 cm ^-1 to 900cm ^-1 in a,

I _a is the peak intensity in the Fourier transform infrared spectroscopy (FTIR) spectrum 1740cm ^-1 to 1700cm ^-1 1420 cm ^-1 peak intensity compared to 1380cm ^-1 in at by the protective layer. Satisfying Equation 1 means that the protective layer of the polarizing plate hardly contains an acrylate group. In this case, the toughness and hardness of the protective layer are improved compared to the case where the protective layer contains an acrylate group or an acrylic compound.

In addition, stress is generated in the polarizer when stretching the polarizer or the polarizer, and cracks are generated in the polarizer when the polarizer is exposed to high temperatures. In order to prevent this, a protective layer is introduced into the polarizer, but when the protective layer includes an acrylate group or an acrylic compound, the protective layer cannot effectively protect the polarizer, and thus there is a problem that cracks occur in the polarizer at high temperatures.

On the other hand, when the protective layer does not contain an acrylate group or an acrylic compound, and includes an epoxy compound and an oxetane compound, the protective layer effectively protects the polarizer, so that cracking of the polarizer at high temperature can be effectively suppressed. have.

In addition, the polarizing plate according to an exemplary embodiment of the present specification is a cured product of a photocurable composition for a protective layer of a polarizing plate comprising an epoxy compound and an oxetane-based compound, and the thickness of the protective layer is adjusted to be 4 μm to 11 μm. It is possible to effectively prevent yellowing from appearing on the polarizing plate or the protective layer.

In one embodiment of the present specification, [Equation 1] may be represented by the following Equation 1-1 or Equation 1-2. In this case, the toughness and toughness of the protective layer are improved compared to the case where the protective layer contains an acrylate group or an acrylic compound.

[Equation 1-1]

[Equation 1-2]

In one embodiment of the present specification, the thickness of the protective layer is 4 μm to 11 μm, preferably 5 μm to 10 μm, and more preferably 6 μm to 8 μm. When the thickness of the protective layer is smaller than the above range, there is a fear that the strength or high temperature durability of the protective layer may be lowered, and when it exceeds the above range, it is not suitable in terms of thinning of the polarizing plate, and the yellowness of the protective layer is greatly increased. there is a problem. Therefore, the polarizing plate of the present specification has an effect of controlling the thickness of the protective layer to the above range to suppress the yellowness of the protective layer from rising.

In one embodiment of the present specification, the yellowness (Yp) of the protective layer may be 1 or less, preferably 0.9 or less, and more preferably 0.8 or less. When the numerical range is satisfied, it has an advantage of suppressing the deterioration of the optical properties of the polarizing plate by yellowing generated in the protective layer.

In one embodiment of the present specification, the change in yellowness (ΔYp) calculated by Equation 2 below is 1 or less, preferably 0.9 or less, and more preferably 0.8 or less.

[Equation 2]

Yellowness change: △ Yp = Ybf-Ybi

In Formula 2, Ybi is the yellowness of the polarizer,

Ybf is the yellowness of the protective layer when the polarizing plate is left for 48 hours at 25 ° C and 40% relative humidity.

In the present specification, the Ybi is the yellowness of the polarizer, and means a yellowness measurement value of the polarizer itself without a protective layer.

In the present specification, ΔYp is a difference between the yellowness (Ybf) of the polarizing plate on which the protective layer is formed and the yellowness (Ybi) of the polarizing plate on which the protective layer is not formed, and means the yellowness (Yp) of the protective layer itself. can do. In addition, the yellowness (Ybi) of the polarizing plate on which the protective layer is not formed may calculate the yellowness of the polarizer itself on which the protective layer is not laminated and use the result.

In the present specification, the yellowness can be measured using a light spectrometer (V-7100, manufactured by JASCO).

When a protective film is directly formed on a conventional polyvinyl alcohol-based stretched type polyvinyl alcohol-based polarizer, tearing of the polarizer is caused by stress caused by the shrinkage of the polarizer at high temperatures compared to the case where a protective substrate is applied to both sides as in the past. It was difficult to solve the problem that occurred. In addition, in order to prevent the problem of deterioration of the optical properties of the polarizing plate according to the protective substrate, there has been a demand for a property without a phase difference and without yellowing.

Therefore, in order to form a protective film directly on the polarizer, the polarizer

Physical properties of a level capable of withstanding stress caused by shrinkage are required. As a protective film satisfying these properties, a UV-curable cationic coating layer is mainly used. In the case of the cationic coating layer, a photoinitiator and a photosensitizer are mainly used to improve the degree of curing, and in this process, a problem that the optical properties of the polarizing plate is deteriorated due to yellowing of the cured product.

In one embodiment of the present specification, the thermal expansion coefficient at 80 ° C of the protective layer is 100 ppm / K or less, 85 ppm / K or less, 10 ppm / K or more, 100 ppm / K or less, or 10 ppm / K or more and 85 ppm / K or less.

In one embodiment of the present specification, the thermal expansion coefficient measured at a temperature of less than 80 ° C of the protective layer is 100 ppm / K or less, 85 ppm / K or less, 10 ppm / K or more, 100 ppm / K or less, or 10 ppm It may be / K or more and 85 ppm / K or less.

In one embodiment of the present specification, the thermal expansion coefficient measured at a temperature of greater than 40 ° C and less than 80 ° C of the protective layer is 100 ppm / K or less, 85 ppm / K or less, 10 ppm / K or more and 100 ppm / K or less, Or 10 ppm / K or more and 85 ppm / K or less.

In one embodiment of the present specification, the thermal expansion coefficient at 70 ° C of the protective layer is 100 ppm / K or less, 85 ppm / K or less, 10 ppm / K or more, 100 ppm / K or less, or 10 ppm / K or more and 85 ppm / K or less.

In one embodiment of the present specification, the thermal expansion coefficient at 60 ° C of the protective layer is 100 ppm / K or less, 85 ppm / K or less, 10 ppm / K or more, 100 ppm / K or less, or 10 ppm / K or more and 85 ppm / K or less.

 When the thermal expansion coefficient of the protective layer satisfies the above range, there is an advantage of effectively suppressing the occurrence of cracks in the polarizing plate in a heat shock resistant environment.

The method for measuring the coefficient of thermal expansion is not particularly limited, for example, a size of 6 mm in width and 10 mm in length of a cured specimen having a thickness of 50 μm prepared by applying a photocurable composition having the same composition as the protective layer. Cut to, and measure the change in length while maintaining the tension load at 0.05N, starting at 30 ℃ and rising to 150 ℃. At this time, the rate of temperature rise is 5 ° C / min, and after the measurement is completed, the thermal expansion coefficient (CTE) value is calculated as the changed length from 40 ° C to the target temperature. The target temperature is 80 ° C or less than 80 ° C, for example, 70 ° C or 60 ° C.

In one embodiment of the present specification, the glass transition temperature (Tg) of the protective layer is 90 ° C or more and 170 ° C or less, preferably 100 ° C or more and 150 ° C or less, and more preferably 100 ° C or more and 130 ° C or less . When the glass transition temperature of the protective layer satisfies the above numerical range, there is an advantage that the physical properties of the protective layer can be maintained under a high temperature environment.

The glass transition temperature of the protective layer is coated on a release film (for example, polyethylene terephthalate film) with a thickness of 6 to 7 μm, cured by irradiating with ultraviolet rays, and then the release film is removed, and the specimen is 5 to 10 mg. It is taken and measured through differential scanning calorimetry (DSC). At this time, the measurement temperature is increased from the starting temperature of 25 ° C to 150 ° C at a heating rate of 5 ° C / min, and the heat flow is measured to measure the glass transition temperature at the inflection point.

Protective layer

The polarizing plate according to the exemplary embodiment of the present specification includes a protective layer directly formed on one or both surfaces of the polarizer. Since the polarizer is vulnerable to external shock, a conventional polarizing plate includes a polarizer and a protective film adhesively bonded to both surfaces. In such a case, there is a problem that the thickness of the polarizing plate is increased by the thickness of the protective film attached.

However, the polarizing plate according to an exemplary embodiment of the present specification includes a protective layer provided on one or both surfaces of the polarizer, so that a separate protective film is not included, or the thickness is significantly reduced by including the protective film on only one surface of the polarizer. Provided is a polarizing plate capable of cost reduction. Accordingly, it is possible to implement a thin film and light weight image display device.

In one embodiment of the present specification, the protective layer is for supporting and protecting the polarizer, and may be formed by a method well known in the art.

Each of the protective layers of the polarizing plate according to the exemplary embodiment of the present specification may be in direct contact with the polarizer. Direct contact with one or both surfaces of the polarizer means that the polarizer and the protective layer contact without intervening an adhesive layer. That is, the protective layer according to the present specification is formed directly on the polarizer without the adhesive layer, thereby providing a thin polarizing plate.

Each of the protective layers of the polarizing plate according to an exemplary embodiment of the present specification may be in direct contact with both sides of the polarizer.

In one embodiment of the present specification, the protective layer may be provided on both sides of the polarizer.

The protective layer of the polarizing plate according to the exemplary embodiment of the present specification has an effect capable of suppressing the occurrence of cracks in the polarizer under harsh environments while protecting the polarizer.

In one embodiment of the present specification, the storage modulus of the protective layer at 80 ° C is 1,500 Mpa or more, 1,500 Mpa or more, 10,000 Mpa or less, preferably 1800 Mpa or more and 8,000 Mpa or less, and more preferably 2,000 Mpa or more and 7,000 Mpa or more Is below. When the storage elastic modulus of the protective layer satisfies the above numerical range, stress applied to the polarizer is effectively suppressed, thereby effectively suppressing crack generation of the polarizer due to shrinkage or expansion of the polarizer in a high temperature or high humidity environment. In addition, adhesion to the polarizer is improved. Thus, by suppressing shrinkage and expansion of the polarizing plate at high temperature, when the polarizing plate is applied to a liquid crystal panel or the like, light leakage can be prevented from occurring, and there is an advantage of exhibiting excellent adhesion. Particularly, when the storage modulus of the protective layer at 80 ° C is 2,000 Mpa or more and 7,000 Mpa or less, the shrinkage of the polarizing plate at high temperature is effectively suppressed, so that generation of polarizer cracks can be effectively suppressed.

The storage elastic modulus of the protective layer is applied to a release film (eg, polyethylene terephthalate film) with a photocurable composition having the same composition as the protective layer with a thickness of 50 μm, and irradiated with ultraviolet light under conditions of a light amount of 1000 mJ / cm ² or higher. After curing, the release film is removed, the specimen is laser cut to a constant size, and then measured through DMA. At this time, the measured temperature was measured from the starting temperature of -30 ℃ to a heating rate of 5 ℃ / min to 160 ℃ while measuring the storage elastic modulus when straining with a strain of 10%, and the storage elastic modulus at 80 ℃ Values were recorded.

In one embodiment of the present specification, the tensile modulus of elasticity of the protective layer at 25 ° C is 1,700 Mpa or more, preferably 1,800 Mpa or more, and more preferably 2,000 Mpa or more. When the tensile elastic modulus of the protective layer satisfies the above numerical range, the stress applied to the polarizer is effectively suppressed, thereby effectively suppressing the occurrence of cracks in the polarizer due to shrinkage or expansion of the polarizer in a high temperature or high humidity environment. In addition, adhesion to the polarizer is improved. Thus, by suppressing shrinkage and expansion of the polarizing plate at high temperature, when the polarizing plate is applied to a liquid crystal panel or the like, light leakage can be prevented from occurring, and there is an advantage of exhibiting excellent adhesion.

The tensile modulus of elasticity of the protective layer is applied to a release film (eg, polyethylene terephthalate film) having a composition having the same composition as the protective layer with a thickness of 100 μm, and cured by irradiating with ultraviolet light under conditions of a light amount of 1000 mJ / cm ² or higher. Then, the release film is removed, and the specimen is regularly laser cut to a width of 10 mm, and then measured through a universal testing machine (UTM). At this time, the measurement temperature is 25 ° C., and the measurement length is 50 mm. The tensile speed is 50 mm / min, and the tensile modulus is obtained through the SS (Stress-Strain) curve obtained by uniformly stretching. The tensile modulus is obtained by multiplying the initial slope of the SS curve by 100.

In one embodiment of the present specification, when the polarizing plate is left at 80 ° C for 4 hours or more, a contraction force of any one or more of an absorption axis direction (MD direction) and a transmission axis direction (TD direction) may be 3N to 10N. When satisfying the above range, it is possible to minimize the occurrence of cracks in the polarizer during thermal shock. At this time, the standing time may be 4 hours or 5 hours.

In one embodiment of the present specification, when the polarizing plate is left at 80 ° C for 4 hours or more, the contraction force in the absorption axis direction (MD direction) is 7N to 9N. When satisfying the above range, it is possible to minimize the occurrence of cracks in the polarizer during thermal shock.

In one embodiment of the present specification, when the polarizing plate is left at 80 ° C for 4 hours or more, the contraction force in the transmission axis direction (TD direction) is 4N to 9N. When satisfying the above range, it is possible to minimize the occurrence of cracks in the polarizer during thermal shock.

The shrinking force is 2mm (transmission axis direction) × 50mm (absorption axis direction) cut the polarizing plate, the target distance is set to 15mm, and is left in an isothermal state at 80 ℃ for 4 hours or more DMA Q800 (Dynamic mechanical analyzer, TA company) to measure the contraction force in the MD or TD direction. At this time, in order to keep the polarizing plate flat before the measurement, the minimum load was measured over the thickness direction of the polarizer.

In one embodiment of the present specification, the polarizing plate satisfies Expression A below. When the polarizing plate satisfies Equation A below, since the difference in shrinking force according to each region of the polarizing plate is small, it can be applied to a large image display device.

[Equation A]

In the above formula A,

The L _c is the contraction force of a region corresponding to a circular area of 1 cm in diameter with the center of the polarizing plate as the origin,

The L _e is a shrinking force of the polarizing plate in a region corresponding to a circular area of 1 cm in diameter, which is in contact with two edge portions that meet at each vertex of the polarizing plate,

The L _i is the average shrinking force in the absorption axis direction (MD direction) or the transmission axis direction (TD direction) of the polarizer; Alternatively, it is the average shrinkage force in the absorption axis direction (MD direction) or transmission axis direction (TD direction) of the polarizing plate.

In one embodiment of the present specification, Equation A may be represented by Equation A-1 or Equation A-2 below.

[Equation A-1]

[Equation A-2]

In one embodiment of the present specification, a method for satisfying the tensile modulus, the storage modulus, and the coefficient of thermal expansion of the protective layer is not particularly limited, and for example, the glass transition temperature in the photocurable composition for forming the protective layer ( Tg) may be included in a photopolymerizable compound having a high content, or a method of increasing the integrated light amount.

In one embodiment of the present specification, the protective layer is preferably formed of a photocurable composition. As described above, when the protective layer is a curable resin layer formed from a photocurable composition, the manufacturing method is simple, and further, there is an advantage of excellent adhesion between the protective layer and the polarizer. In addition, the durability of the polarizing plate can be further improved.

In one embodiment of the present specification, the photocurable composition is not particularly limited as long as the coefficient of thermal expansion satisfies the above range, and may be, for example, a photocurable composition including an epoxy compound and an oxetane-based compound. In this case, there is an advantage that it is excellent in heat resistance and water resistance, and can be attached to a polarizer without an adhesive layer in place of a protective film that essentially requires a conventional adhesive.

In one embodiment of the present specification, the photocurable composition for the polarizing plate protective layer includes an epoxy compound and an oxetane-based compound.

In one embodiment of the present specification, the epoxy compound includes an alicyclic epoxy compound. The alicyclic epoxy compound means a compound containing at least one epoxidized aliphatic ring group. Since the alicyclic epoxy compound has a relatively high glass transition temperature, it is preferable to lower the coefficient of thermal expansion of the protective layer and increase the storage modulus. Thus, it serves to realize excellent durability under high temperature or high humidity environment after curing.

As the alicyclic epoxy compound, an epoxycyclohexylmethyl epoxycyclohexanecarboxylate-based compound represented by the following [Chemical Formula 1] may be exemplified.

[Formula 1]

In Formula 1, R ₁ and R ₂ each independently represent a hydrogen or an alkyl group.

The term alkyl group used herein means a straight-chain, branched or cyclic alkyl group having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, unless otherwise specified. The alkyl group may be optionally substituted by one or more substituents, or may be in an unsubstituted state.

Another example of the alicyclic epoxy compound includes an epoxycyclohexane carboxylate-based compound of an alkanediol represented by the following formula (2).

[Formula 2]

In Formula A, R ₃ and R ₄ each independently represent a hydrogen or alkyl group, and n represents an integer of 2 to 20.

Moreover, as another example of an alicyclic epoxy compound, the epoxy cyclohexylmethyl ester type compound of dicarboxylic acid represented by following formula (3) is mentioned.

[Formula 3]

In Formula 3, R ₅ and R ₆ each independently represent a hydrogen or an alkyl group, and p represents an integer of 2 to 20.

Another example of the alicyclic epoxy compound includes an epoxycyclohexylmethyl ether-based compound of polyethylene glycol represented by the following formula (4).

[Formula 4]

In Formula 4, R ₇ and R ₈ each independently represent a hydrogen or an alkyl group, and q represents an integer of 2 to 20.

Another example of the alicyclic epoxy compound includes an epoxycyclohexylmethyl ether-based compound of an alkanediol represented by the following formula (5).

[Formula 5]

In Formula 5, R ₉ and R ₁₀ each independently represent a hydrogen or alkyl group, and r represents an integer of 2 to 20.

As another example of the alicyclic epoxy compound, there may be mentioned a diepoxycitrispyro compound represented by the following formula (6).

[Formula 6]

In Formula 6, R ₁₁ and R ₁₂ each independently represent a hydrogen or an alkyl group.

Another example of the alicyclic epoxy compound is a diepoxymonospiro compound represented by the following formula (7).

[Formula 7]

In Formula 7, R ₁₃ and R ₁₄ each independently represent a hydrogen or an alkyl group.

As another example of the alicyclic epoxy compound, there may be mentioned a vinylcyclohexene diepoxide compound represented by the following formula (8).

[Formula 8]

In Formula 8, R ₁₅ represents hydrogen or an alkyl group.

Another example of the alicyclic epoxy compound is an epoxy cyclopentyl ether compound represented by the following formula (9).

[Formula 9]

In Formula 9, R ₁₆ and R ₁₇ each independently represent a hydrogen or an alkyl group.

Another example of the alicyclic epoxy compound includes a diepoxy tricyclo decane compound represented by the following formula (10).

[Formula 10]

In the formula (10), R ₁₈ represents hydrogen or an alkyl group.

In one embodiment of the present specification, as the alicyclic epoxy compound, more specifically, an epoxycyclohexylmethyl epoxycyclohexane carboxylate compound, an alkanediol epoxycyclohexane carboxylate compound, and a dicarboxylic acid epoxycyclohexylmethyl ester compound Or, it is preferable to use an epoxycyclohexylmethyl ether compound of alkanediol, 7-oxabicyclo [4,1,0] heptan-3-carboxylic acid and (7-oxa-bicyclo [4,1,0] hepto -3-yl) esterified with methanol (a compound in which R ₁ and R ₂ in Formula 1 are hydrogen); Ester of 4-methyl-7-oxabicyclo [4,1,0] heptan-3-carboxylic acid with (4-methyl-7-oxa-bicyclo [4,1,0] hepto-3-yl) methanol Cargo (in Formula 1, R ₁ is 4-CH ₃ and R ₂ is 4-CH ₃ ); An esterified product of 7-oxabicyclo [4,1,0] heptane-3-carboxylic acid and 1,2-ethanediol (a compound wherein R ₃ and R ₄ in the formula (A) is hydrogen and n is 1); (7-oxabicyclo [4,1,0] hepto-3-yl) esterified product of methanol and adipic acid (a compound in which R ₅ and R ₆ in the formula (3) is hydrogen and p is 2); Esterate of (4-methyl-7-oxabicyclo [4,1,0] hepto-3-yl) methanol and adipic acid (R ₅ and R ₆ in Formula 3 above are 4-CH ₃ , p is 2 compounds); And (7-oxabicyclo [4,1,0] hepto-3-yl) methanol and an etherified product of 1,2-ethanediol (R ₉ and R ₁₀ in Formula 5 are hydrogen and r is 1) ) May be preferably used one or more selected from the group consisting of), but is not limited thereto.

In one embodiment of the present specification, the weight ratio of the epoxy compound and the oxetane-based compound is 9: 1 to 1: 9, and the preferred weight ratio is 9: 1 to 7: 3. When the numerical range of the weight ratio of the epoxy compound and the oxetane-based compound is as described above, the glass transition temperature of the composition may be maintained high, and the strength of the protective layer after curing is greatly improved. In addition, when the above range is satisfied, there is an advantage that the storage elastic modulus of the protective layer after curing is excellent.

In one embodiment of the present specification, the epoxy compound is preferably 50 to 90 parts by weight, more preferably 70 to 90 parts by weight based on 100 parts by weight of the total composition. When the above range is satisfied, it is easy to satisfy the storage elastic modulus and thermal expansion coefficient of the above-described protective layer, and the glass transition temperature after curing of the entire composition is maintained high, and the composition has excellent adhesive strength to the polarizer.

In one embodiment of the present specification, the epoxy compound includes a glycidyl ether type epoxy compound. The glycidyl ether type epoxy compound means an epoxy compound containing at least one glycidyl ether group.

In one embodiment of the present specification, the glycidyl ether type epoxy compound includes, for example, novolac epoxy, bisphenol A-based epoxy, bisphenol F-based epoxy, brominated bisphenol epoxy, n-butyl glycidyl ether, ali Patic glycidyl ether (12 to 14 carbon atoms), 2-ethylhexylglycidyl ether, phenyl glycidyl ether, o-cresyl glycidyl ether, nonyl phenyl glycidyl ether, ethylene glycol diglycol Cidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane polyglycidyl ether, polyethylene glycol di Ricidyl ether or glycerin triglycidyl ether and the like can be exemplified, and also hydrogenated compounds of glycidyl ethers or aromatic epoxy compounds having a cyclic aliphatic skeleton such as 1,4-cyclohexanedimethanol diglycidyl ether and the like Etc. can be exemplified, preferably a glycidyl ether having a cyclic aliphatic skeleton, preferably a cyclic aliphatic skeleton having 3 to 20 carbon atoms, preferably 3 to 16 carbon atoms, more preferably 3 to 12 carbon atoms Glycidyl ether may be used, but is not limited thereto.

In one embodiment of the present specification, the epoxy compound may be a mixture of an alicyclic epoxy compound and a glycidyl ether type epoxy compound.

In one embodiment of the present specification, when the alicyclic epoxy compound and the glycidyl ether type epoxy compound are used in combination, the weight ratio is preferably 3: 1 to 1: 3, and more preferably 2: 1 to 1: 2.

In one embodiment of the present specification, the alicyclic epoxy compound may be included in an amount of 10% to 100% by weight based on the total weight of the epoxy compound, preferably 20% to 80% by weight, more preferably 30% by weight % To 70% by weight. When the above numerical range is satisfied, there is an advantage that the composition can be effectively cured during photocuring.

In one embodiment of the present specification, the glycidyl ether type epoxy compound may be included in an amount of 10% to 60% by weight based on the total weight of the epoxy compound, and preferably 30% to 50% by weight.

In one embodiment of the present specification, the oxetane-based compound is a compound having a 4-membered ring ether in a molecule, but is not limited thereto, 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3 -Ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, di [(3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl- Examples include 3- (2-ethylhexyloxymethyl) oxetane and phenol novolac oxetane. These oxetane compounds can be obtained commercially easily, specifically, Aaron oxetane OXT-101 (manufactured by Doa Kosei Co., Ltd.), Aaron oxetane OXT-121 (manufactured by Doa Kosei Co., Ltd.), Aaron ox And cetane OXT-211 (manufactured by Doa Kosei Co., Ltd.), Aaronoxetane OXT-221 (manufactured by Doa Kosei Co., Ltd.), and aronoxetane OXT-212 (manufactured by Doa Kosei Co., Ltd.).

In one embodiment of the present specification, the oxetane-based compound may be used alone or in mixture, and the content thereof is preferably 10 to 50 parts by weight, and more preferably 10 to 30 parts by weight in 100 parts by weight of the total composition. Do. When the above numerical range is satisfied, there is an advantage that the glass transition temperature and the storage modulus after curing of the entire composition can be kept high, and the viscosity is kept constant to form a protective layer of uniform thickness.

In one embodiment of the present specification, the photocurable composition for the polarizing plate protective layer may further include a photoinitiator.

In one embodiment of the present specification, examples of the photoinitiator include alpha-hydroxyketone compounds (ex. IRGACURE 184, IRGACURE 500, IRGACURE 2959, DAROCUR 1173; Ciba Specialty Chemicals (product)); Phenylglyoxylate-based compounds (ex. IRGACURE 754, DAROCUR MBF; Ciba Specialty Chemicals (manufactured)); Benzyl dimethyl ketal compounds (ex. IRGACURE 651; Ciba Specialty Chemicals (manufactured)); α-aminoketone compounds (ex. IRGACURE 369, IRGACURE 907, IRGACURE 1300; Ciba Specialty Chemicals (manufactured)); Monoacylphosphine-based compounds (MAPO) (ex. DAROCUR TPO; Ciba Specialty Chemicals (manufactured)); Bisacylphosphene compound (BAPO) (ex. IRGACURE 819, IRGACURE 819DW; Ciba Specialty Chemicals (manufactured)); Phosphine oxide compounds (ex. IRGACURE 2100; Ciba Specialty Chemicals (manufactured)); Metallocene compounds (ex. IRGACURE 784; Ciba Specialty Chemicals (manufactured)); Iodonium salt (ex. IRGACURE 250; Ciba Specialty Chemicals (manufactured)); And mixtures of one or more of the above (ex. DAROCUR 4265, IRGACURE 2022, IRGACURE 1300, IRGACURE 2005, IRGACURE 2010, IRGACURE 2020; Ciba Specialty Chemicals (manufactured)). In the present invention, one or more of the above may be used, but is not limited thereto.

In one embodiment of the present specification, the photoinitiator may be included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the photocurable composition for a polarizing plate protective layer. When the photoinitiator is included in the content of the numerical range, it is not included, or the curing progresses better than when the numerical range is not satisfied, and there is an advantage that adhesion is more improved.

In one embodiment of the present specification, the photocurable composition for the polarizing plate protective layer may further include 1 to 5 parts by weight of a cationic polymerization initiator relative to 100 parts by weight of the total composition.

In one embodiment of the present specification, the photocurable composition for the polarizing plate protective layer preferably has a viscosity of 50 cPs or more and 200 cPs or less at 25 ° C, for example, 50 cPs to 130 cPs or less at 25 ° C. When the viscosity of the composition satisfies the above numerical range, the thickness of the protective layer can be thinly formed, and it has the advantage of excellent workability because it has a low viscosity.

The viscosity is measured at room temperature (25 ° C) using a spindle 18 using a Brookfield viscometer (manufactured by Brook Field). At this time, the amount of the composition is 6.5 to 10mL is appropriate, and to avoid exposure to light for a long time, the stabilized value is measured within 5 minutes.

In one embodiment of the present specification, the photocurable composition for the polarizing plate protective layer is a dye, a pigment, an epoxy resin, an ultraviolet stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, an antifoaming agent, a surfactant, a photosensitizer, and a plasticizer as necessary. One or more additives selected from the group consisting may be further included.

In one embodiment of the present specification, the additive may be included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the photocurable composition for a polarizing plate protective layer.

In one embodiment of the present specification, the method of forming the protective layer is not particularly limited, and may be formed by a method well known in the art. For example, the photocurable composition for the polarizing plate protective layer is applied to one surface of the polarizer by a coating method well known in the art, such as spin coating, bar coating, roll coating, gravure coating, blade coating, and the like to form a protective layer. Then, it may be performed by a method of curing through ultraviolet irradiation. For example, it can be performed by a method of irradiating ultraviolet rays that are irradiated light using an ultraviolet irradiation device.

In one embodiment of the present specification, the wavelength of the ultraviolet rays may be 100 nm to 400 nm, preferably 320 nm to 400 nm.

In one embodiment of the present specification, the light amount of the irradiated light may be 100 mJ / cm ² to 1,000 mJ / cm ² , preferably 500 mJ / cm ² to 1,000 mJ / cm ² .

In one embodiment of the present specification, the irradiation time of the irradiation light may be 1 second to 10 minutes, preferably 2 seconds to 30 seconds. When the irradiation time range is satisfied, it is possible to prevent excessive heat from being transmitted from the light source, thereby minimizing generation of travel wrinkles in the polarizer.

Protection film

In this specification, the protective layer is provided on one surface of the polarizer,

As a polarizing plate is a protective film is attached to the other side of the surface provided with a protective layer of the polarizer via an adhesive layer,

It provides a polarizing plate having a tensile modulus of elasticity at 25 ℃ of the protective film is 1700 Mpa or more.

According to FIG. 2, in the present specification, a protective film 20 is provided on one surface of the polarizer 10 and an adhesive layer is applied to the other surface of the surface provided with the protective layer 20 of the polarizer 10 as a medium. It provides a polarizing plate is attached (30).

In the present specification, when the protective layer is formed on one surface of the polarizer, a separate protective film may be attached via an adhesive layer to support and protect the polarizer on the opposite side of the surface on which the protective layer is formed.

In one embodiment of the present specification, the protective film is for supporting and protecting the polarizer, protective films of various materials generally known in the art, for example, polyethylene terephthalate (PET) Films, cycloolefin polymer (COP) films, and the like can be used. Among these, it is particularly preferable to use polyethylene terephthalate when considering optical properties, durability, economical efficiency, and the like.

In one embodiment of the present specification, the tensile modulus of elasticity of the protective film at 25 ° C may be 1,800 Mpa or more and 10,000 Mpa or less, preferably 2,000 Mpa or more and 8,000 Mpa or less, and more preferably 3,000 Mpa or more and 7,000 Mpa or less. When the numerical range is satisfied, the protective effect of the polarizer of the protective film may be increased. Specifically, the tearing phenomenon of the polarizer due to stress generated by the shrinkage or expansion of the polarizer in a high temperature or high humidity environment can be prevented.

In one embodiment of the present specification, the polarizer and the protective film are coated by using a roll coater, a gravure coater, a bar coater, a knife coater or a capillary coater, etc., to coat the polarizer adhesive composition on the surface of the polarizer or the protective film. Subsequently, they may be heated by laminating with a laminating roll, or by laminating by pressing at room temperature, or by UV irradiation after laminating. The polarizing plate adhesive composition will be described later.

Adhesive layer

In one embodiment of the present specification, the adhesive layer is a cured product of the adhesive composition. As described above, when the adhesive layer is a curable resin layer formed of a photocurable composition, the manufacturing method is simple, and further has an advantage of excellent adhesion to a protective film. In addition, the durability of the polarizing plate can be further improved.

In one embodiment of the present specification, the coefficient of thermal expansion of the adhesive layer at 40 ° C to 80 ° C is 130 ppm / K or less. When the coefficient of thermal expansion exceeds 130 ppm / K, there is a problem that cracking of the polarizing plate occurs in a heat shock resistant environment.

In one embodiment of the present specification, the storage modulus of the adhesive layer at 80 ° C may be 100 Mpa or more and 1,800 Mpa or less, preferably 150 Mpa or more and 1,300 Mpa or less, and more preferably 180 Mpa or more and 500 Mpa or less. When the above range is satisfied, there is an effect that adhesion of the adhesive layer is increased and peeling of the protective film does not easily occur. In particular, if it exceeds the above range, the storage modulus is too high, and the adhesive force is poor, so that it cannot function sufficiently as an adhesive layer.

The storage elastic modulus of the adhesive layer is coated on a release film (for example, polyethylene terephthalate film) with a photocurable composition having the same composition as the adhesive layer with a thickness of 50 μm, and irradiated with ultraviolet light under conditions of a light amount of 1000 mJ / cm ² or higher. After curing, the release film is removed, the specimen is laser cut to a constant size, and then measured through DMA. At this time, the measured temperature was measured from the starting temperature of -30 ℃ to a heating rate of 5 ℃ / min to 160 ℃ while measuring the storage elastic modulus when straining with a strain of 10%, and the storage elastic modulus at 80 ℃ Values were recorded.

In one embodiment of the present specification, the photocurable adhesive composition is not particularly limited as long as the coefficient of thermal expansion satisfies the above range, and may be, for example, a photocurable composition comprising an epoxy compound and an oxetane-based compound.

In one embodiment of the present specification, the epoxy compound may use at least one of an alicyclic epoxy compound and a glycidyl ether type epoxy compound, preferably an alicyclic epoxy compound and a glycidyl ether type epoxy compound Mixtures of can be used. The glycidyl ether type epoxy compound means an epoxy compound containing at least one glycidyl ether group.

In one embodiment of the present specification, the glycidyl ether type epoxy compound includes, for example, novolac epoxy, bisphenol A-based epoxy, bisphenol F-based epoxy, brominated bisphenol epoxy, n-butyl glycidyl ether, ali Patic glycidyl ether (12 to 14 carbon atoms), 2-ethylhexylglycidyl ether, phenyl glycidyl ether, o-cresyl glycidyl ether, nonyl phenyl glycidyl ether, ethylene glycol diglycol Cidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane polyglycidyl ether, polyethylene glycol di Ricidyl ether or glycerin triglycidyl ether and the like can be exemplified, and also hydrogenated compounds of glycidyl ethers or aromatic epoxy compounds having a cyclic aliphatic skeleton such as 1,4-cyclohexanedimethanol diglycidyl ether and the like Etc. can be exemplified, preferably a glycidyl ether having a cyclic aliphatic skeleton, preferably a cyclic aliphatic skeleton having 3 to 20 carbon atoms, preferably 3 to 16 carbon atoms, more preferably 3 to 12 carbon atoms Glycidyl ether may be used, but is not limited thereto.

In one embodiment of the present specification, when the alicyclic epoxy compound and the glycidyl ether type epoxy compound are used in combination, the weight ratio is preferably 3: 1 to 1: 3, and more preferably 2: 1 to 1: 2.

In one embodiment of the present specification, the alicyclic epoxy compound may be included in an amount of 10% to 50% by weight based on the total weight of the epoxy compound, and preferably 20% to 40% by weight. When the above numerical range is satisfied, there is an advantage that the composition can be effectively cured during photocuring.

In one embodiment of the present specification, the glycidyl ether type epoxy compound may be included in an amount of 10% to 60% by weight based on the total weight of the epoxy compound, and preferably 30% to 50% by weight.

In one embodiment of the present specification, examples of the epoxy compound include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis (3,4-epoxycyclohexylmethyl) adipate, 3 Caprolactone modified product of, 4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, esterified product of polyvalent carboxylic acid and 3,4-epoxycyclohexylmethyl alcohol or caprolactone modified product, alicyclic at the terminal Silicone compound having an epoxy group, diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol A bromide, phenol novolak type epoxy resin, cresol novolak type epoxy resin, biphenyl Type epoxy resin, terephthalic acid diglycidyl ester, phthalic acid diglycidyl ester, addition reaction product of terminal carboxylic acid polybutadiene and bisphenol A type epoxy resin, dicyclopentadiene Oxide, limonene dioxide, 4-vinylcyclohexene dioxide, polyethylene glycol (3 or more repetitions) diglycidyl ether, polypropylene glycol (3 or more repetitions) diglycidyl ether, polytetramethylene glycol (3 or more repetitions) ) Diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, epoxidized vegetable oil, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl Triethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, polybutadienediglycidyl ether of both terminal hydroxyl groups, internal epoxide of polybutadiene, styrene-butadiene air Compounds in which the double bond of the coalescence is partially epoxidized [for example, "epopend" manufactured by Daicel Chemical Industry Co., Ltd.], and the isoprene unit of the block copolymer of ethylene-butylene copolymer and polyisoprene And some epoxidized compounds (eg, “L-207” manufactured by KRATON).

In one embodiment of the present specification, the adhesive composition may further include a curable component, and the curable component is a compound having a plurality of polymerizable double bonds such as a compound having a (meth) acryloyl group and a vinyl group. Can be For example, tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, EO modified di Glycerin Tetraacrylate, Aaronix M-220 (manufactured by Toa Synthetic), Lightacrylate 1,9ND-A (manufactured by Kyoeisha Chemicals), Lightacrylate DGE-4A (manufactured by Kyoeisha Chemicals), Lightacrylate DCP And -A (manufactured by Kyoeisha Chemical Co., Ltd.), SR-531 (manufactured by Sartomer), and CD-536 (manufactured by Sartomer). Moreover, various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, and various (meth) acrylate-based monomers may be mentioned as necessary. When including the curable component, it is possible to increase the curing rate, there is an advantage that a high level of curing is possible even with a low light amount.

In one embodiment of the present specification, the polarizer adhesive composition may further include a photoinitiator. The description of the photoinitiator is the same as that of the photoinitiator included in the above-described protective layer.

In one embodiment of the present specification, the polarizing plate adhesive composition is a dye, a pigment, an epoxy resin, an ultraviolet stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, an antifoaming agent, a surfactant, a photosensitizer, and a plasticizer, if necessary. It may further include one or more additives selected. The description of the additive is the same as that of the additive included in the protective layer described above.

Polarizer

In one embodiment of the present specification, the polarizer may be a polarizer well known in the art, for example, a film made of polyvinyl alcohol (PVA) including iodine or a dichroic dye. The polarizer may be prepared by dyeing an iodine or dichroic dye on a polyvinyl alcohol film, but the manufacturing method thereof is not particularly limited.

In the present specification, the polarizer means a state that does not include a protective layer (or protective film), and the polarizer means a state that includes a polarizer and a protective layer (or protective film).

In one embodiment of the present specification, the polarizer may have a thickness of 5 μm to 40 μm, more preferably 5 μm to 25 μm. If the thickness of the polarizer is thinner than the above range, the optical properties may deteriorate, and if it is thicker than the above range, the shrinkage of the polarizer at a low temperature (about -30 ° C) may be large, which may be a problem in durability related to heat of the entire polarizing plate.

In one embodiment of the present specification, the polarizer is a polyvinyl alcohol-based film. The polyvinyl alcohol-based film can be used without particular limitation as long as it includes a polyvinyl alcohol resin or a derivative thereof. At this time, as the derivative of the polyvinyl alcohol resin, but not limited to, polyvinyl formal resin, polyvinyl acetal resin and the like. Alternatively, the polyvinyl alcohol-based film is a commercially available polyvinyl alcohol-based film commonly used in the manufacture of polarizers in the art, for example, P30, PE30, PE60 from Gurayre, M2000, M3000, M6000 of Japan Synthetic, etc. You can also use

In one embodiment of the present specification, the polymerization degree of the polyvinyl alcohol-based film is 1,000 to 10,000, preferably 1,500 to 5,000. When the polymerization degree satisfies the above range, molecular movement is free, and it can be flexibly mixed with iodine or dichroic dye.

Adhesive layer

In one embodiment of the present specification, the polarizing plate further includes an adhesive layer on the protective layer. This is for attachment to an optical film, such as a display panel or retardation film.

According to FIG. 3, in the present specification, a protective film 20 is provided on one surface of the polarizer 10 and an adhesive layer is applied to the other surface of the surface provided with the protective layer 20 of the polarizer 10 as a medium. 30 is attached, and further includes an adhesive layer 40 provided on the protective layer 20.

In one embodiment of the present specification, the adhesive layer may be formed using various adhesives well known in the art, and the type is not particularly limited. For example, the adhesive layer is a rubber-based adhesive, an acrylic adhesive, a silicone-based adhesive, a urethane-based adhesive, a polyvinyl alcohol-based adhesive, a polyvinylpyrrolidone-based adhesive, a polyacrylamide-based adhesive, a cellulose-based adhesive, a vinyl alkyl ether-based adhesive, etc. It can be formed using. Among these, when considering transparency, heat resistance, and the like, it is particularly preferable to use an acrylic adhesive.

In one embodiment of the present specification, the pressure-sensitive adhesive layer may be formed by applying a pressure-sensitive adhesive on the top of the protective layer, and after applying the pressure-sensitive adhesive on a release sheet and drying it, the pressure-sensitive adhesive sheet prepared by drying is attached to the top of the protective layer It may be formed in a manner.

Image display device

The present specification provides an image display device including the polarizing plate described above.

In one embodiment of the present specification, the polarizing plate may be usefully applied to an image display device such as a liquid crystal display device.

In one embodiment of the present specification, the image display device includes a liquid crystal panel; An upper polarizing plate provided on an upper surface of the liquid crystal panel; And a lower polarizing plate provided on the lower surface of the liquid crystal panel.

FIG. 4 illustrates an image display device having a polarizing plate 100 on one surface of the liquid crystal panel 200. According to FIG. 4, one surface of the liquid crystal panel 200 and the polarizing plate 100 are adhered through the adhesive layer 40 of the polarizing plate 100.

In one embodiment of the present specification, the upper polarizing plate is the polarizing plate described above.

In one embodiment of the present specification, the lower polarizing plate is the polarizing plate described above.

In one embodiment of the present specification, the upper polarizing plate and the lower polarizing plate are the polarizing plates described above.

In one embodiment of the present specification, the type of the liquid crystal panel is not particularly limited. For example, a passive matrix type panel such as a twisted nematic (TN) type, a super twisted nematic (STN) type, a ferroelectic (F) type, or a polymer dispersed (PD) type; An active matrix panel such as a two-terminal type or a three-terminal type; All well-known panels, such as an in-plane switching (IPS) panel and a vertical alignment (VA) panel, can be applied. In addition, other configurations constituting the liquid crystal display device, for example, types of upper and lower substrates (ex. Color filter substrates or array substrates) are also not particularly limited, and configurations known in this field may be employed without limitation. You can.

Hereinafter, the present specification will be described in more detail through examples. However, the following examples are intended to illustrate the present specification, and the scope of the present specification is not limited thereby.

<Preparation of photocurable composition>

<Production Examples A1 and A2: Preparation of a protective layer composition not containing an acrylate group>

80 parts by weight of 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexanecarboxylate (trade name Celloxide-2021) and 3-ethyl-3-[(3-ethyloxetan-3-yl) Methoxymethyl] oxetane (Doa Gosei Aaron Oxetane OXT-221) 100 parts by weight of a photocurable composition containing 20 parts by weight of Irgacure 250 as a photoinitiator and 3 parts by weight of ESACURE ITX as a photosensitizer and photocurable by adding 1 part by weight of ESACURE ITX Composition A1 was prepared.

In the same manner, a composition A2 having the composition of Table 1 below was prepared. The content of the photoinitiator and photosensitizer is based on the total weight of the remaining epoxy compound and oxetane compound, excluding the photoinitiator and photosensitizer.

division Epoxy compounds Oxetane compounds Photoinitiator Photosensitizer Alicyclic epoxy compound Glycidyl ether type epoxy compound compound product name CEL2021P CHDMDGE OXT-221 IRG-250 ESCURE ITX Composition A1 80 - 20 3 One Composition A2 42 28 30 3 One

* CEL2021P: 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexanecarboxylate CHDMDGE: 1,4-cyclohexyl dimethanol diglycidyl ether

OXT-221: 3-ethyl-3-[(3-ethyloxetan-3-yl) methoxymethyl] oxetane (Doase Gosei Aaron Oxetane OXT-221)

IRG-250: Iodonium salt (Product name: Irgacure-250, manufactured by CIBA)

<Production Examples B1 to B9: Preparation of a protective layer composition containing an acrylate group>

1) Preparation Examples B1 to B8

A protective layer composition including an acrylate group was prepared according to the composition of Table 2 below. The content of the photoinitiator and photosensitizer is based on the total weight of the remaining epoxy compound, oxetane compound and acrylic compound, excluding the photoinitiator and photosensitizer.

division Epoxy compounds Oxetane compounds Acrylic compound Photoinitiator Photosensitizer product name C2021P OXT221 DCPDA PVEEA VEEA Irgacure 250 Irgacure 819 ESCURE ITX Preparation Example B1 Composition B1 56 14 30 0 0 1.85 One 0.74 Preparation Example B2 Composition B2 48 12 40 0 0 1.58 1.5 0.63 Preparation Example B3 Composition B3 56 14 0 30 0 1.85 One 0.74 Preparation Example B4 Composition B4 48 12 0 30 10 1.58 1.5 0.63 Preparation Example B5 Composition B5 56 14 0 20 10 1.85 One 0.74 Preparation Example B6 Composition B6 56 14 15 15 0 1.85 One 0.74 Preparation Example B7 Composition B7 56 14 15 5 10 1.85 One 0.74 Preparation Example B8 Composition B8 56 14 5 15 10 1.85 One 0.74

* DCPDA: Dicyclopentadiene acrylate

VEEA: 2- (2-Vinyloxyethoxy) ethyl acrylate

IRG-819: (Bis (2,4,6-trimethylbenzoyl) -phenylphosphineoxide)

2) Production Example B9

100 parts by weight of 4-hydroxybutyl acrylate (4-Hydroxybutyl Acrylate: manufactured by Osaka Chemical Industries) and 20 parts by weight of Tris (2-acryloyloxyethyl) Isocyanurate (product name: FA-731A, manufactured by Hitachi Chemical) 100 parts by weight A photocurable composition B9 was prepared by adding 3 parts by weight of IRG-819 (Bis (2,4,6-trimethylbenzoyl) -phenylphosphineoxide) as a photoinitiator.

<Production Examples C1 to C3: Preparation of adhesive composition>

An adhesive composition was prepared according to the composition of Table 3 below. In Table 3, the content of the photoinitiator and photosensitizer is based on the total weight of the remaining epoxy compound, oxetane compound, and acrylic compound, excluding the photoinitiator and photosensitizer.

division Epoxy compounds Oxetane compounds Acrylic compound Photoinitiator Photosensitizer Alicyclic epoxy compound Glycidyl ether type epoxy compound Product or compound name CEL2021P CHDMDGE OXT-221 OXT-212 Nonanediol diacrylate - ESCURE ITX Composition C1 30 40 20 - 10 3 (IRG-250) One Composition C2 35 20 5 40 - 2 One Composition C3 30 40 20 - 10 5 (CPI110P) -

* CPI-100P: Photoinitiator manufactured by San Apro

OXT-212: 3-ethyl-3-[(2-ethylhexyloxy) methyl] oxetane (Toagosei Aaron Oxetane OXT-212)

<Examples and Comparative Examples: Preparation of polarizing plate>

<Example 1>-Structure of the protective film / polarizing plate / protective layer

After dyeing the dichroic dye on the polyvinyl alcohol (PVA) -based resin film, a polarizer was prepared by stretching and crosslinking in a certain direction. As an adhesive layer, a photocurable composition C1 was coated on one surface of the prepared polarizer using a roll coater, a PET film was laminated as a protective film, and then irradiated with ultraviolet rays to cure the adhesive layer. The thickness of the adhesive layer formed by the cured photocurable composition was 2 μm.

Subsequently, a photocurable composition A1 was coated on the other surface of the surface on which the protective film of the polarizer was laminated using a bar coater or a roll coater, and a protective layer having a thickness of 6 μm was formed by irradiating ultraviolet rays to prepare a polarizing plate. The polarizing plate has a structure in which a protective film is laminated on one surface of the polarizer via an adhesive layer of 2 μm, and a protective layer is directly formed on the other surface of the surface on which the protective film of the polarizer is laminated.

<Example 2>

A polarizing plate was manufactured in the same manner as in Example 1, except that the thickness of the protective layer was 5 μm.

<Example 3>

A polarizing plate was manufactured in the same manner as in Example 1, except that the thickness of the protective layer was 8 μm.

<Example 4>

A polarizing plate was manufactured in the same manner as in Example 1, except that the thickness of the protective layer was 10 μm.

<Example 5>

A polarizing plate was manufactured in the same manner as in Example 1, except that the photocurable composition A2 was used instead of the photocurable composition A1 as a material for the protective layer.

<Example 6>

A polarizing plate was manufactured in the same manner as in Example 5, except that the photocurable composition A2 was used instead of the photocurable composition C1 as a material for the adhesive layer.

<Comparative Example 1>

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the photocurable composition C1 was used instead of the photocurable composition A1 as a material for the protective layer.

<Comparative Example 2>

A polarizing plate was manufactured in the same manner as in Example 1, except that instead of the adhesive composition C1, the photocurable composition C2 was used as a material for the adhesive layer.

<Comparative Example 3- PET protective film / adhesive layer / PVA / adhesive layer / TAC protective film>

A photocurable composition A2 was applied to one surface of the same polarizer used in Example 1 using a roll coater to have a thickness of 2 μm, and a corona-treated PET film of 80 μm thickness was bonded. The adhesive composition C3 was applied to the other surface of the surface on which the photocurable composition A2 of the polarizer was applied using a roll coater to a thickness of 1 μm, and a 25 μm thick TAC film (manufactured by Fuji Corporation) was bonded, and irradiated with ultraviolet rays to The photocurable composition A2 and the adhesive composition C3 were cured to prepare a polarizing plate.

<Comparative Example 4>

A polarizing plate was manufactured in the same manner as in Comparative Example 3, except that an acrylic film having a thickness of 40 μm (manufactured by Rinken) was used instead of the TAC film.

<Comparative Example 5>-Structure of protective film / polarizing plate / protective layer

A polarizing plate was manufactured in the same manner as in Example 1, except that the thickness of the protective layer was 20 μm.

<Comparative Example 6>

A polarizing plate was manufactured in the same manner as in Example 1, except that the thickness of the protective layer was 30 μm.

<Comparative Example 7 to Comparative Example 15>

A polarizing plate was prepared in the same manner as in Example 1, except that photocurable compositions B1 to 98 were used instead of photocurable composition 1 as a material for the protective layer.

The composition and thickness of the protective layer of the polarizing plates of the prepared examples and comparative examples are shown in Table 4 below.

division layer Furtherance thickness Example 1 Protective layer Composition A1 6㎛ Adhesive layer Composition C1 2㎛ Example 2 Protective layer Composition A1 5㎛ Example 3 Protective layer Composition A1 8㎛ Example 4 Protective layer Composition A1 10㎛ Example 5 Protective layer Composition A2 6㎛ Adhesive layer Composition C1 2㎛ Example 6 Protective layer Composition A2 6㎛ Adhesive layer Composition A2 2㎛ Comparative Example 1 Protective layer Composition C1 6㎛ Comparative Example 2 Protective layer Composition A1 6㎛ Adhesive layer Composition C2 2㎛ Comparative Example 3 1st protective film PET 80㎛ First adhesive layer Composition A2 2㎛ Second adhesive layer Composition C3 1㎛ 2nd protective film TAC 25㎛ Comparative Example 4 1st protective film PET 80㎛ First adhesive layer Composition A2 2㎛ Second adhesive layer Composition C3 1㎛ 2nd protective film Acrylic film 40㎛ Comparative Example 5 Protective layer Composition A1 20㎛ Comparative Example 6 Protective layer Composition A1 30㎛ Comparative Example 7 Protective layer Composition B1 6㎛ Comparative Example 8 Protective layer Composition B2 6㎛ Comparative Example 9 Protective layer Composition B3 6㎛ Comparative Example 10 Protective layer Composition B4 6㎛ Comparative Example 11 Protective layer Composition B5 6㎛ Comparative Example 12 Protective layer Composition B6 6㎛ Comparative Example 13 Protective layer Composition B7 6㎛ Comparative Example 14 Protective layer Composition B8 6㎛ Comparative Example 15 Protective layer Composition B9 6㎛

The adhesive layers of Examples 2 to 4, Comparative Examples 1 and 5 to 15 are 2 µm thick adhesive layers using the adhesive composition C1 in the same manner as in Example 1.

<Experimental Example>

<Method for measuring physical properties>

1. Tensile modulus measurement

After coating the polyethylene terephthalate film with a thickness of 100 μm using the photo-curable composition prepared in the preparation example, and curing it by irradiating with ultraviolet light under conditions of 1000 mJ / cm ² or more, the release film is removed, and the specimen is 10 mm wide. After laser cutting with constant, it is measured through UTM (Universal Testing Machine). At this time, the measurement temperature is set to room temperature (25 ° C), and the measurement length is 50 mm. The tensile modulus is obtained through the SS (Stress-Strain) curve obtained by constantly pulling the tensile speed at 50 mm / min. The tensile modulus is obtained by multiplying the initial slope of the SS curve by 100.

2. Storage modulus measurement

The polarizing plates prepared in Examples and Comparative Examples were cut using a laser having a size of 5.3 mm in width and 4.5 cm in length. Thereafter, a storage elastic modulus was measured using a DMA (Dynamic Mechanical Analyzer). The measurement mode was Multi-Frequency-Strain, and the temperature was increased from -30 ℃ to 160 ℃ at 5 ℃ per minute.

3. Measurement of thermal expansion coefficient

The photocurable composition prepared in the preparation example was coated between release PETs, and then cured under the same curing conditions as in the above example so that the final thickness was 50 μm. Then, the cured product separated from the release PET was cut into 6 mm wide and 10 mm long. Then, using a TMA, while maintaining a tension load of 0.05N, the temperature was increased at a rate of 5 ° C / min at a rate of temperature increase from 30 ° C to 150 ° C, and the changed length was measured to measure the coefficient of thermal expansion (CTE).

4. High temperature acceleration evaluation

A protective film was laminated on a polarizer using the photocurable composition prepared in the above-mentioned preparation example, and cured in the same manner as in the example. Subsequently, a polarizing plate was prepared by coating on the polarizer in the same manner as in the above Examples and Comparative Examples, except that cracking was caused in the polarizer by scratching with a load of 300 g using a blunt pencil.

Subsequently, after cutting the polarizing plate to a width of 6 mm and a length of 10 mm, and then standing at 80 ° C. for 100 hours, the cracks were cracked due to the shrinkage of the polarizer, and light was leaked, and the number of cracks leaking out of all cracks was calculated. , The crack generation rate in the polarizing plate was derived.

In addition, when the size of the polarizing plate was changed and applied to a 55-inch panel, crack incidence in the polarizing plate was measured.

* Crack incidence: Number of cracks leaking / Total number of cracks x 100 (%)

5. Evaluation of adhesion

A protective film was laminated on a polarizer using the photocurable composition prepared in the above-mentioned preparation example, and cured in the same manner as in the example. Thereafter, when the peeling force of the protective film and the polarizer is 2 N / cm or more, it is good, and if it is less than that, it is considered defective.

6. Analysis of protective layer composition

Examples and Comparative Examples By performing FTIR analysis on the protective layer of the polarizing plate, the peak areas at 1720 cm ^-1 , 1410 cm ^-1 and 910 cm ^-1 were analyzed and are shown in Table 5 below. In addition, the FTIR spectrum for Comparative Example 8 is shown in Fig. 5, and the FTIR spectrum for Example 1 is shown in Fig. 6, respectively. The protective layer composition was measured before and after curing. In addition, the range of Equation 1 was measured and shown in Table 5 below.

division Peak area Equation 1 1720 cm ^-1
(C = O bond) Ia (with peak intensity of 1410 cm ^-1 , acrylic) Ie (with peak intensity of 910 cm ^-1 , epoxy) Example 1 3.38 0 0.06 One Example 2 6.83 0 0.06 One Comparative Example 7 8.05 0.47 0.34 0.07 Comparative Example 8 8.46 0.61 0.03 0.05 Comparative Example 9 7.18 0.28 0.03 0.1 Comparative Example 10 7.29 0.38 0.02 0.05 Comparative Example 11 7.60 0.85 0.03 0.08 Comparative Example 12 7.00 0.28 0.03 0.1 Comparative Example 13 7.40 0.37 0.03 0.08 Comparative Example 14 7.16 0.33 0.03 0.08

In the formula 1, with a peak at 1740cm ^-1 to 1700cm ^-1 select a peak at 1720 cm ^-1, and each select a peak at 1410 cm ^-1 to the peak at 1420 cm ^-1 to 1380cm ^-1 The ratio of the peak intensity at 1410 cm ^-1 to the peak intensity at 1720 cm ^-1 was calculated as Ie.

Further, in the equation 1, a peak of 1740cm ^-1 to 1700cm ^-1 in the selected peak at 1720 cm ^-1 and the peak at 910 cm ^-1 to the peak at 920 cm ^-1 to 900cm ^-1, respectively By selecting, the ratio of the peak intensity at 910 cm ^-1 to the peak intensity at 1720 cm ^-1 was calculated as Ie.

The peak intensity corresponds to the peak area of the FTIR spectrum. The peak area can be derived by direct integration. Alternatively, one peak of the FTIR spectrum is assumed to be a Gaussian distribution, and the peak area is calculated from the product of the height of the peak and a half value width.

From the above results, it can be seen that the polarizing plate protective layers of Examples 1 and 2 did not include an acrylate group, but the polarizing plate protective layers of Comparative Examples 7 to 14 contained an acrylate group.

7. Polarizer shrinkage test

The shrinkage force of the polarizing plate of Example 1 was tested.

The shrinking force is 2mm (transmission axis direction) × 50mm (absorption axis direction) cut the polarizing plate, the target distance is set to 15mm, and is left in an isothermal state at 80 ℃ for 4 hours or more DMA Q800 (Dynamic mechanical analyzer, TA company) to measure the contraction force in the MD or TD direction. At this time, in order to keep the polarizing plate flat before the measurement, the minimum load was measured over the thickness direction of the polarizer.

The measurement was repeated 8 times, and the results are shown in Table 6 below. The average shrinkage force in the MD direction was 8.03 N and 6.62 N.

division Shrinking force (unit: N) MD direction TD direction 1 time 7.9 8.09 Episode 2 7.73 8.28 3rd time 7.9 8.09 Episode 4 7.73 8.28 Episode 5 8.12 6.45 Episode 6 8.11 3.96 Episode 7 9.06 6.44 Episode 8 7.58 3.4 Average 8.03 N 6.62 N

<Experimental results depending on whether the protective layer contains acrylate>

The durability / heat resistance test and adhesion test according to the presence or absence of acrylate in the protective layer are shown in Table 7 below.

From this result, it was confirmed that the polarizing plate protective layer does not contain an acrylate group (Examples 1 and 2) and has a high temperature durability and adhesion compared to the case of containing (Comparative Examples 7 to 14).

That is, since the polarizing plate protective layer of the embodiment includes an epoxy compound and an oxetane compound instead of an acrylic compound, since the polarizer protective effect by the protective layer is excellent, even when the shrinking force of the polarizing plate or the polarizer is large, cracks occur in the polarizer under a high temperature environment It has the advantage of minimizing things.

division Crack incidence as a result of accelerated high temperature evaluation (unit size) Adhesion test Example 1 0% Good Example 2 10% Good Comparative Example 7 65% Bad Comparative Example 8 80% Bad Comparative Example 9 50% Bad Comparative Example 10 80% Bad Comparative Example 11 70% Bad Comparative Example 12 50% Bad Comparative Example 13 70% Bad Comparative Example 14 70% Bad

<Yellowing test>

For the yellowing phenomenon test according to the protective layer stacking of Example 1, a sample was prepared. Specifically, the same photocurable composition A1 as the composition used to form the protective layer of Example 1 on the TAC film (manufactured by Fuji Corporation, thickness 25 µm) was applied using a bar coater or roll coater, and an ultraviolet irradiation device A protective layer having a thickness of 6 μm was formed by irradiating UV light at 1,000 mJ / cm ² with. Thereafter, after standing for 48 hours under a temperature of 25 ° C and a relative humidity (RH) of 40%, the yellowness (b *) value of the polarizing plate was measured using a light spectrometer (V-7100, manufactured by JASCO). For accuracy, the average value was calculated after 3 repeated measurements.

The rest of the Examples and Comparative Examples were also measured in the same way and summarized in Table 8 below.

The yellowness (Ybi) of the polarizing plate and the polarizer before lamination of the protective layer was 2.3 to 2.4.

division Protective layer thickness Yellowness of polarizing plate after standing (Ybf) Yellowness change
(△ Yp = Ybf-Ybi) Example 1 6 μm 3.003 0.641 Example 2 5 μm 2.932 0.542 Example 3 8 μm 3.112 0.75 Example 4 10 μm 3.275 0.913 Example 5 6 μm 2.737 0.347 Comparative Example 5 20 μm 3.774 1.384 Comparative Example 6 30 μm 4.351 1.989

From the above results, it was confirmed that in the case of Comparative Examples 5 and 6 in which the thickness of the protective layer exceeded 10 µm, even if the composition of the protective layer was the same as in Examples 1 to 4, the yellowness increased significantly.

<Experimental results according to the composition of the protective layer>

The composition of the Examples and Comparative Examples and the experimental results are shown in Table 9 below.

division Floor division @ 80 ℃
Coefficient of thermal expansion
(ppm / K) @ 25 ℃ tensile
Modulus of elasticity @ 80 ℃ storage elastic modulus Polarizer
Crack incidence Example 1 Protective layer 82.33 2200Mpa 2500MPa 0% Adhesive layer 130.89 900 MPa 800 MPa Example 2 Protective layer 82.33 2200Ma 2500MPa 5% Adhesive layer 130.89 900 MPa 800 MPa Example 3 Protective layer 82.33 2200Ma 2500MPa 0% Adhesive layer 130.89 900 MPa 800 MPa Example 4 Protective layer 82.33 2200MPa 2500MPa 0% Adhesive layer 130.89 900 MPa 800 MPa Example 5 Protective layer 99.87 2000MPa 1900MPa 10% Adhesive layer 130.89 900 MPa 800 MPa Example 6 Protective layer 99.87 2000MPa 1900MPa 5% Adhesive layer 99.87 2000MPa 1900MPa Comparative Example 1 Protective layer 130.89 900 MPa 800 MPa 50% Adhesive layer 130.89 900 MPa 800 MPa Comparative Example 2 Protective layer 130.89 900 MPa 800 MPa 100% Adhesive layer 1063.6 50MPa 70MPa Comparative Example 15 Protective layer 1,000 or more -(Not implemented) 300 Mpa or less 100% Adhesive layer 130.89 900 MPa 800 MPa

The polarizing plates according to Examples 1 to 6 had a polarizing plate crack incidence of less than 10%, but it was confirmed that a number of polarizing plate cracks were generated in the polarizing plates according to Comparative Examples 1 and 2 and Comparative Example 15. Examples 1 to 6, in which the protective layer was directly formed on the polarizer, showed excellent results while the thickness of the protective layer was thin (5 to 10 µm) and little incidence of cracks in the polarizing plate. This is because the thermal expansion coefficient of the protective layer is low, and the tensile modulus and storage modulus are excellent, effectively suppressing the polarizer from expanding or contracting at high temperatures.

On the other hand, in the case of the polarizing plates according to Comparative Examples 1, 2 and Comparative Example 15, since the thermal expansion coefficient of the protective layer directly formed on the polarizer is high, it is impossible to suppress the polarizer from expanding or contracting at high temperatures, and cracks are generated in the polarizer. I could confirm that.

Particularly, the polarizing plate of Comparative Example 15 contains an acrylic compound in the protective layer. In this case, because the thermal expansion coefficient of the protective layer is too high (1,000 ppm / K or more), and the storage elastic modulus is low (300 Mpa or less), high temperature acceleration evaluation As a result, it can be seen that many cracks were generated.

<Experimental results according to the laminated structure of the polarizing plate>

Table 10 below shows a polarizing plate having structures of 'protective film / adhesive layer / PVA / protective layer' (Examples 1 to 6) and a polarizing plate having a structure of 'protective film / adhesive layer / PVA / adhesive layer / protective film' ( The polarizing plates of Comparative Examples 3 and 4) were compared with each other, and the properties of the protective layers formed directly on the polarizers of Examples 1 to 6 and the protective films formed through the adhesive layer on the polarizing plates of Comparative Examples 3 and 4 were compared. will be.

division Thickness (㎛) 80 ℃
Coefficient of thermal expansion
(ppm / K) 80 ℃ storage modulus (Mpa) Polarizer
Crack incidence Example 1 Protective layer 6 82.33 2500 0% Example 2 Protective layer 5 82.33 2500 5% Example 3 Protective layer 8 82.33 2500 0% Example 4 Protective layer 10 82.33 2500 0% Example 5 Protective layer 6 99.87 1900 10% Example 6 Protective layer 6 99.87 1900 5% Comparative Example 3 Protection film 40 88 1800 80% Adhesive layer One 223 700 Comparative Example 4 Protection film 40 83 1900 80% Adhesive layer One 223 700

In the case of the polarizing plates according to Comparative Examples 3 and 4, although the total thickness of the adhesive layer and the protective film was thick, a large number of polarizing plate cracks were generated, resulting in poor durability.

On the other hand, in the case of the polarizing plates according to Examples 1 to 6, the thickness of the protective layer directly formed on the polarizer was 5 to 10 µm, but the polarization plate crack incidence was low.

This is because the thermal expansion coefficient of the protective layer formed directly on the polarizer of the polarizing plates according to Examples 1 to 6 is low, but the storage elastic modulus is excellent. This is because even if there is no separate protective film, the shrinkage or expansion phenomenon at a high temperature of the polarizer is effectively suppressed.

On the other hand, in the case of the polarizing plates according to Comparative Examples 3 and 4, even if the thermal expansion coefficient value of the protective film is low, since the thermal expansion coefficient of the adhesive layer directly formed on the polarizer is high, the shrinkage or expansion phenomenon at high temperature of the polarizer is effectively suppressed. Because it did not.

10: polarizer
20: protective layer
30: protective film
40: adhesive layer
100: polarizer
200: liquid crystal panel

Claims (15)

Polarizer; And
A protective layer provided in direct contact with the polarizer on one or both sides of the polarizer,
The protective layer is a cured product of a photocurable composition for a polarizing plate protective layer comprising an epoxy compound, an oxetane-based compound, a photoinitiator and a photosensitizer,
The content of the photoinitiator and the photosensitizer is 0.01 parts by weight to 5 parts by weight based on 100 parts by weight of the photocurable composition for the protective layer of the polarizing plate, respectively.
The thickness of the protective layer is 4㎛ to 11㎛,
In the spectrum by the Fourier transform infrared spectroscopy (FTIR) of the protective layer, the following equation 1 is satisfied,
A polarizing plate having a yellowness change (ΔYp) calculated by Equation 2 below 1 or less:
[Equation 1]

[Equation 2]
Yellowness change: △ Yp = Ybf-Ybi
In Equation 1,
I _e is the ratio of the peak intensity in the protective layer Fourier transform infrared spectroscopy (FTIR) 1740cm ^-1 to 1700cm ^-1 in the spectra due to the peak intensity compared to 920 cm ^-1 to 900cm ^-1 in a,
I _a is the intensity of the peak in a Fourier transform infrared spectroscopy (FTIR) spectrum 1740cm ^-1 to 1700cm ^-1 1420 cm ^-1 peak intensity compared to 1380cm ^-1 in at by the protective layer,
In Formula 2, Ybi is the yellowness of the polarizer,
Ybf is the yellowness of the protective layer when the polarizing plate is left at 25 ° C and 40% relative humidity for 48 hours. delete delete The polarizing plate according to claim 1, wherein the thermal expansion coefficient of the protective layer at 80 ° C. is 100 ppm / K or less. The method according to claim 1, wherein the glass transition temperature (Tg) of the protective layer is 90 ° C or more and 170 ° C or less. The polarizing plate according to claim 1, wherein the storage layer has a storage modulus at 80 ° C. of 1,500 Mpa or higher. The polarizing plate according to claim 1, wherein the protective layer has a tensile modulus of elasticity at 25 ° C. of 1,700 Mpa or more. The method according to claim 1, When the polarizing plate is left at 80 ° C for 4 hours or more, the shrinking force of at least one of the absorption axis direction (MD direction) and the transmission axis direction (TD direction) is 3N to 10N. The polarizing plate according to claim 1, which satisfies Expression A below.
[Equation A]

In the above formula A,
The L _c is the contraction force of a region corresponding to a circular area of 1 cm in diameter with the center of the polarizing plate as the origin,
The L _e is a shrinking force of the polarizing plate in a region corresponding to a circular area of 1 cm in diameter, which is in contact with two edge portions that meet at each vertex of the polarizing plate,
The L _i is the average shrinking force in the absorption axis direction (MD direction) or the transmission axis direction (TD direction) of the polarizer; Alternatively, it is the average shrinkage force in the absorption axis direction (MD direction) or transmission axis direction (TD direction) of the polarizing plate. The method according to claim 1, wherein the epoxy compound is a polarizing plate comprising an alicyclic epoxy compound. The method according to claim 1, wherein the weight ratio of the epoxy compound and the oxetane-based compound is 9: 1 to 1: 9 polarizing plate. The method according to claim 1, The protective layer is provided on one surface of the polarizer,
As a polarizing plate is a protective film is attached to the other side of the surface provided with a protective layer of the polarizer via an adhesive layer,
A polarizing plate having a tensile modulus of elasticity at 25 ° C of the protective film of 1700 Mpa or more. The method according to claim 1, wherein the protective layer is provided on both sides of the polarizer. The method according to claim 1, The polarizing plate further comprises an adhesive layer on the opposite surface of the surface opposite to the polarizer of the protective layer. An image display device comprising the polarizing plate of any one of claims 1 and 4 to 14.

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